Category Archives: Space

Monsters of the Cosmos: Black holes

by Chris Phoenix Clarke

“Now I am become Death, the destroyer of worlds” – Bhagavad Gita, Verse 32, Chapter 11

BLACK HOLES are the most terrifying, yet least understood features of the cosmos.  It is thought that a supermassive black hole — that is, one millions of times the mass of our sun — resides at the centre of every adult galaxy (including our own), and that quasars — the brightest and most distant (and, indeed, oldest) objects known in the Universe — might be the source of their turbulent creation.

I hope to take you on a journey into the heart of these mythical structures:  from violent births in the hearts of collapsing stars, to primordial beasts as old as the Universe itself; from white holes and wormholes, to escape velocities and event horizons.  Perhaps what follows might even make you question your very understanding of the fabric of reality, and indeed the Universe, itself.

So, first things first; how do they form?

To put it bluntly our Sun is a bit nondescript.  It’s a bit average.  For all its toiling fury and life-enabling radiation, the Sun is the cosmic equivalent of a vodka orange – nothing too exciting, but it’s hardly a  boring glass of soda water either.  When it dies it will quite uneventfully shed its outer layers and compress into a white dwarf star, seeing out the remainder of its days glowing gradually fainter as the aeons pass by.  Much like an ageing Guinness drinker propping up the local pub, our Sun is certainly no vomiting teenage binge drinker like its more massive counterparts.  In stark contrast, these stars getting on 15 times the mass of the Sun are simply too large to become white dwarfs and end their days in a quite spectacular fashion:  their respective cores undergoing cataclysmic implosions of truly astronomical proportions; the collapse causing the violent expulsion of each of the star’s outer layers into space, leaving behind dense and strange objects so mind-boggling it almost defies belief.

A 'feeding' black hole devouring a nearby star.
Artist’s depiction of a ‘feeding’ black hole devouring a nearby star.  Image credit: NASA

These objects are known as stellar black holes — something that challenges our most fundamental of intuitions on the most grandest of scales.

Smaller stars undergo nuclear fusion in their cores at a much slower rate than giant stars, ensuring that they burn less brightly and live a good while longer.  The comparison of giant stars being the ‘rock gods’ of the Universe is usually a good way of looking at it.   Rather than living a life of excess and partying and possibly dying from an overdose, our Sun is the much more sedate and conservative type, blending in with the crowd and living well into the age where beige clothing is appealing.  But leaving the alcohol-related anthropomorphic analogies aside for a moment, like everything else in the Universe, stars have finite lifetimes

When stars between about 0.5 and 1.4 solar masses pop their celestial clogs they implode, leaving behind the aforementioned white dwarf star; the fatal core collapse having been halted by something known as electron degeneracy pressure*.  This is the outward pressure caused by the electrons in the core obeying a quantum mechanical rule applying to all fermions (a family of particle of which an electron is a part of) called Pauli’s exclusion principle.  It states that no two fermions with the same energy level can occupy the same space, meaning that the core can only reach a certain density before the electrons simply cannot get any closer together, for fear of treading on each other’s sub-atomic toes, so to speak.

*as a point of interest, it is worth noting that the recent supernova in galaxy M82 is thought to have been a white dwarf star that gained mass from a binary companion (another star in mutual orbit around the other).  The result was a core-collapse supernova that is currently visible in the night sky at the time of writing [25th January 2014].

Then again, when stars with cores above this critical mass (otherwise known as the Chandrasekhar limit) die, their cores initiate a collapse of such energy that each electron decides it’s ‘had quite enough of this s**t’ and attaches itself to the nearest available proton — much like a toddler clinging to their mother’s leg — to form a neutron, enabling the collapse to continue to even more compact volumes and densities.  Then, just like the electrons before, the neutrons themselves create their own outward pressure for similar reasons and the collapse is halted.  The resulting object is known as a neutron star.  So dense is this stellar remnant (the star having been well over 2 million km in diameter before,  is now just 15 km wide) that one teaspoon-full would weigh as much as mount Everest!   (see previous blog ‘Pulsars, magnetars and neutron stars‘).

Artist's impression of a supernova explosion.
Artist’s impression of a supernova explosion.  Image credit: NASA

But it’s really the heavy-set kebab munchers with cores in excess of 15 solar masses that, via their own immense gravity, crush down so violently that even the neutron pressure cannot tolerate the force, and the result of this super-sized implosion is the object known as the stellar black hole**.

**another way for a stellar black hole to form is for an existing neutron star to gain mass; to accrete matter from somewhere else.  This can be achieved in a binary star system containing a red giant star and a neutron star, for example, with the latter gravitationally ripping off streams of gas and plasma from the former –- thus increasing its mass.  If the critical mass is breached then core-collapse will start and an implosion into a black hole is inevitable.

That’s a bit racist!  Why are they called black holes?

Considering the exotic nature of these awesome monsters, they are actually quite aptly named.  Far removed from the dubiously-coined terms for the sub-atomic quark particles (such as ‘up’, ‘down’, ‘charmed’ and ‘strange’ flavours), or the way biologists seem to over complicate the naming of even the most simple of life’s processes, black holes are essentially black and do represent a cosmic hole of sorts.

According to Einstein’s seminal paper on general relativity (see previous blog: ‘Once upon a spacetime‘), space is inextricably linked with time and in the presence of gravity space is curved.  In short, this means that space and time are no longer two separate entities, but instead exist as one conjoined entity known as spacetime, and that wherever mass is found, spacetime bends in towards it.  The larger the mass, the more the curvature of the spacetime around it.  The familiar analogy of a bowling ball being placed upon a taught sheet of rubber is one way to visualise it, with the rubber bending in as the weight of the bowling ball warps the sheet.  Analogous to a marble being rolled towards the bowling ball would be the planets in orbit around the Sun.

The curvature of spacetime around a mass is the definition of gravity itself; it’s the act of ‘falling’ into this curved space that gives the illusion of a force pulling something in towards it.

Such is the curvature of spacetime, or gravity, generated by a black hole that the situation arises in which nothing can escape its attraction once ‘fallen in’ (this, the event horizon, will be explained more in a second).  Light, in all its unparalleled performance, is nigh-on fast enough to free itself, meaning that, to quote The Eagles – Hotel California: ‘you can check out any time you like, but you can never leave’, rendering the black hole forever invisible to our curious eyes.  It is, to describe it as Terry Pratchett might, so dark that it is devoid of colour; it is the blackest of all really black things***

***sometimes when a black hole is ‘feeding’, the matter being sucked in forms a super-heated accretion disc around the perimeter of the event horizon.  The process can also produce jets of radiation expelled at the poles.  This enables the black hole to have its effects on in-falling matter directly observed, but still not those within the actual black hole itself.

Okay, but what actually is a black hole?

The key ingredient to black holes is their titanic gravity .  When a supergiant star dies and undergoes core-collapse as part of a supernova explosion, what’s left is an object so compact that it’s been hitherto impossible for human minds to contemplate.  Indeed, the predictions of Einstein’s general relativity suggest that these remnants are actually infinitely dense but occupy a space of zero volume — that is, they are infinitely small.  This ‘singularity’ as it is known, is clearly counter-intuitive; how can something be infinitely dense and yet take up no space whatsoever?  Moreover, the physics break down as soon as these infinite numbers start being introduced — usually meaning some part of the theory is wrong or incomplete — and that, in fact, there is probably no singularity at all — just something we are yet to understand.

So in answer to the question ‘what is a black hole?’, and as far as is currently understood, black holes are regions of space containing an object that is infinitely dense, but occupies no volume.  It is infinitely small — a singularity.  It sounds almost retarded, but we can actually calculate the mass of a black hole by its effect on nearby gas and stars — thus defining a particular value for its mass even though the object itself has zero volume and is infinitely small!  You might well be thinking that something is amiss here — that scientists need to go back and carefully review their life choices, and you wouldn’t be the first, or indeed last, to share this opinion!

The truth is no one knows; it is simply conjecture (more on the ‘funkier’ theories later on).  One of the aims of physics in the last 100 years has been to unite our two best theories of the Universe — general relativity and quantum mechanics — to give one overriding explanation of how everything works.  We’ll then see what the mathematics has to say about black holes and their dubious singularities…

‘Event horizon’ is a 1997 film starring Laurence Fishburne, what does it have to do with black holes?

The event horizon of a black hole.
The event horizon of a black hole.  Image credit: Answers magazine

What we can establish by using Einstein’s theory of general relativity is how black holes warp, or bend, the surrounding spacetime to such an extent that nothing can escape the pull upon breaching a certain critical distance from the centre.  This radius is known as the event horizon, or Schwarzschild radius, and it is the distance at which the escape velocity of the black hole equals the speed of light.  This ‘point of no return’ at which a black hole’s escape velocity is equal to the speed of light (300,000 km per second) is easily understood by picturing a fast-flowing river that becomes ever-more difficult to paddle your kayak against, until the current becomes so great that your heroic paddling counts for naught as the kayak tumbles over the waterfall.  Analogous to the waterfall is the black hole’s event horizon.  Simply put, it is the maximum distance from the black hole’s centre inside of which an outside observer cannot see into; events inside this zone are forever unknowable****

****Stephen Hawking recently argued that the event horizon is not actually a well-defined boundary as Einstein’s general relativity would have us believe but, instead, more of a fuzzy, fluctuating area of spacetime caused by quantum effects (Nature, 2014).

Just as a rocket being launched from Earth needs to hit a certain speed to be able to counter the effects of gravity and travel into space, so too does anything encountering a black hole (if it intends to leave).  This speed is known as the escape velocity.  The gravity generated by the warping of space around the mega-dense black hole is so huge that the required escape speed is in excess of the speed of light.  This means that something would need to travel faster than the speed of light to leave the confines of a black hole, and as light by its very nature cannot travel faster than itself, this poses a problem.  What it actually does is render the inside of the black hole forever black (as light is trapped by the gravity) so no information can ever leave to hit our eyes in order to see it.

If we can’t see them, how do we know they exist?

Due to their inherent blackness it is only possible to infer a black hole’s existence indirectly, that is, the effect they have on surrounding matter, and from doing so it is also possible to determine the mass of the black hole.  The two main indications of a black hole’s existence are the speed of orbiting stars and gas around a central region of space (observed as being empty), accretion disks of orbiting material, and energetic outbursts known as radiation jets.

The G2 gas cloud will encounter our very own supermassive black hole in 2014.
The G2 gas cloud will encounter our very own supermassive black hole in 2014.  Image credit: Sunday Times

A perfect example, potentially at least, is the impending feast of Sagittarius A* — the supermassive black hole at the centre of the Milky Way.  In the coming months leading up to summer 2014, the black hole–some four million times the mass of the Sun–will play host to an incoming gas cloud three times the mass of the Earth  (BBC 2014), tugging at it gravitationally until it rips apart and becomes ‘spaghettified’ as the black hole slowly feeds and devours — dragging the head of the gas cloud inwards faster than the tail, thus causing the metaphor of elongation commonly found in Italian cuisine.  This cosmic banquet has the prospective chance to brighten Sagittarius A* by a factor of 10,000; an event unlikely to occur at such close proximities again for several hundred years, and will allow astronomers and astrophysicists to finally have some light shed on an otherwise very shadowy supermassive spectre at the heart of our very own spiral galaxy.

This event is not too dissimilar to a deep-sea oil rig setting off thousands of flare guns one-by-one in the dead of night — illuminating the  sky for miles around as the location is quite clearly  revealed.  Of course, there’s always the chance things don’t go to plan, such as the gas cloud’s trajectory being slightly off or a small wayward star masquerading behind the veils of the cloud; both possibilities potentially causing the entire mass to career past the black hole rather than being sucked in like vermicelli.  Only time will tell.

Wormholes, white holes and parallel universes

Black holes are bread and butter for science fiction advocates and inventive imaginations.  No more exotic a phenomenon could have been dreamt of, let alone one that is posited to actually be real and considered science fact.  Many wondrously wacky ideas have been exclaimed regarding the ‘insides’ of black holes, and if we’ve learnt anything in science since the days of Copernicus and Newton it’s to never discount any theory as crazy by its merits alone.  It is often said that sufficiently advanced technology is indistinguishable from magic, and the same applies for new discoveries.  No one truly knows what goes on inside a black hole, but I’ve picked perhaps the most hopeful  and altogether enticing of the current bunch of theories, namely: wormholes and white holes.

White holes are the hypothesised opposites of black holes.  They are impossible to enter and can quite happily emit light and matter into Space.  Claimants of this belief hold that at the singularity of a black hole is a white hole doing its reverse thing out into another universe.  If you imagine a sand timer — the opening funnel at the top collects all the sand and directs it down to the centre, at which point it falls out of the opening funnel at the bottom.  Analogous to this is the black hole collecting all light and matter and funnelling it into the singularity, which in actual fact is a white hole spewing it back out into another universe.  Some even go as far to say that white holes are actually the causes of ‘big bangs’, and that our universe is actually a kind of waste product from another universe’s black hole – our big bang having been caused by the associated white hole.

In the immortal words of Wayne’s World — Wayne: “No way!”, Garth: “Way!”

But 1990’s-movie shock aside, it’s no less valid an idea than current standard cosmological models stating that everything in the Universe was created at a single point.

Wormholes, or Einstein-Rosen bridges to go by their proper name, are hypothesised tunnels connecting two regions of spacetime and are an active, ongoing area of theoretical physics research.  There is much debate about what kind of wormhole could exist, but a certain type, at least, is predicted from the equations of Einstein’s general relativity (a theory that has withstood all scrutinies thrown at it, in what is now its 99th year).

Traversing the wormhole's 'throat' can be quicker than light travelling outside the wormhole.
Traversing the wormhole’s ‘throat’ can be quicker than light travelling outside the wormhole.  Image credit: Edobric

Some proponents suggest intra-universe wormholes to be a possibility — that is, tunnels connecting 2 different regions of spacetime in the same universe.  If the geometry of space is curved like many believe, it would therefore be allowable to travel faster than the speed of light, although not in the traditional sense.  It would simply be faster to traverse the wormhole from one location to the other than it would be for light to ‘go the long way around’ by travelling in the spacetime outside the wormhole.  If you imagine sprinting at maximum speed around the side of a mountain to get to the other side, someone walking through a tunnel bored through its centre could conceivably get to the other side before you did.  Of course, light travelling in the wormhole with you would always reach the other location before you did, in the same way as a sprinter running through the tunnel will always beat the person walking.

There’s all sorts of complications with these wormholes, however.  To be traversable they seem to require ‘exotic’ matter in the form of some sort of negative-energy mass in order to stabilise them, and some scientists claim that wormholes can only exist in one direction in the singularities of black holes.  The latter would only bring you out into another region of spacetime inside a different black hole, meaning that you could never escape out past the event horizon in this new region.

The quantum-mechanical
The quantum-mechanical “Schrödinger’s cat” paradox according to the many-worlds interpretation. In this interpretation, every event is a branch point; the cat is both alive and dead, even before the box is opened, but the “alive” and “dead” cats are in different branches of the universe, both of which are equally real, but which do not interact with each other.  Image credit: Christian Schirm

Perhaps a more compelling argument is that of inter-universe wormholes.  These wormholes actually bring the traveller out into another region of spacetime in a parallel universe, resolving certain paradoxes which may arise in intra-universe wormholes, such as time travel and causality violations (the traveller would be brought out into a separate universe that doesn’t interact with the first, so they would never run into said paradoxes).  This theory is an interpretation of quantum mechanics, whereby reality is more like a tree of many branches, where every possible outcome does happen and there is an infinite number of parallel universes.  Standard quantum mechanics (I say standard; there is absolutely nothing orthodox about quantum theory!) uses something called a wavefunction collapse which asserts that before something is observed every outcome is possible, until collapsing into just one reality the moment it is observed.  Schrödinger’s cat being the usual analogy to use at this point, but I’ll refrain from delving any deeper into quantum mechanics here (see picture above).

Quasars and supermassive black holes

Finally we get to the real monsters of the cosmos: supermassive black holes.  It is hard to fathom just how powerful, how huge and how destructive these leviathans of space really are.  It is consensus amongst physicists that one lies at the centre of every adult galaxy and that the formation of these giants is down to the brightest phenomena in the Universe: quasars.

Supermassive black holes range in the order of  a hundred-thousand to a a few-billion times the mass of the Sun, whereas stellar black holes are classified as forming from stars up to about 30 times the mass of the Sun.  Intermediate black holes, as they are known, are strangely lacking from our observations of the cosmos which suggests that the formation of supermassive black holes is fundamentally different to that of stellar black holes.

It is worth mentioning at this point that evidence of supermassive black holes has been observed in the very early universe, implying that their creation is something that occurred during the first generation of galaxies.  Some theories assert that newly-forming galaxies are turbulent and chaotic places and that existing stellar black holes are constantly fed and grow to larger, more intermediate sizes.  They then encounter other black holes doing the same and a kind of cannibalistic black-hole chain-reaction occurs, eventually going on to form one colossal supermassive black hole at the centre of the galaxy.  This cannibal-esque feeding frenzy forms what is known as a quasar — an active galactic nucleus that takes the form of enormous jets of energy being emitted from the edges of the supermassive hole’s event horizon as an orbiting accretion disc of stars, gas and other black holes is fed into the monster’s mouth.

Quasars seem to have been a feature of almost all newly-forming galaxies during the first generation in the early universe.  They are therefore some of the oldest detectable sources of light we have observed — which also make them the most distant.  Such is the energy output of a quasar that it is possible to observe one 28 billion light years away!

Another theory puts forward the existence of primordial supermassive black holes — those that formed as a direct consequence of the extreme pressures of the Big Bang, and would explain the origins of supermassive black holes at the centres of the first galaxies.

So one might say, if some of the previously-stated theories are combined, that a black hole in another universe created a white hole in our Universe (the Big Bang) which, in turn, created the primordial supermassive black holes of the first galaxies.  These eerily-enormous galactic engines allowed for the continued evolution of stars which, themselves, lived out their lives to eventually collapse into stellar black holes.  And so the grand black-hole recycling system goes on and on…  One might even say that black holes are the fundamental mechanism by which our Universe (and, potentially, an infinite amount of other universes) is built upon, and without which, there would be no Universe to reside inside so we could sit here and ponder their importance in the first place.

So it seems that stellar black holes are as ubiquitous in the Universe as they are unusual and, although related in a sense to supermassive black holes, form very differently to their monstrous big brothers.  These celestial older siblings are likely found at the centre of every known galaxy and are perhaps key to the Universe’s evolution and continued survival.  Whatever really lurks in these regions of dark space, whether complicit with current theory or not, will doubtless be, at the very least, just as exotic as the limitations of our intelligence have allowed us to imagine.

Written by Chris Phoenix Clarke, January 2014.

References:

Clarke C.W., 2014. Space City. Available at https://www.facebook.com/Spacecityofficial/posts/581437771950444 [accessed 29th January 2014]

Nature, 2014. Stephen Hawking ‘There are no black holes’. Available at http://www.nature.com/news/stephen-hawking-there-are-no-black-holes-1.14583 [Accessed 29th January 2014]

BBC, 2014. Black hole’s ‘big meal’ could spark fireworks. Available at http://www.bbc.co.uk/news/world-middle-east-25678737 [accessed 29th January 2014]

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Star profile: Betelgeuse

by Chris Phoenix Clarke

Betelgeuse (pronounced ‘betel-jers’) is a red supergiant star around 640 light years away in the constellation of Orion. It is nearly 1000 times larger than the Sun and 20 times more massive; it’s diameter alone would be enough to engulf Mercury, Venus, Earth and Mars and would reach the orbit of Jupiter.

Betelgeuse, as compared to our Sun.
Betelgeuse, as compared to our Sun.

The star is in the final stages of its lifecycle and is expected to go supernova any time between now and the next million years. Upon doing so, Betelgeuse–or at the very least the light from the explosion–will outshine the full Moon and be clearly visible in broad daylight.  Due to the distance involved it is quite possible that Betelguese has already exploded, but we wouldn’t know about it until the light had completed its 640 year journey to Earth!

Doomsayers in 2012 claimed the ensuing gamma-ray burst from the supernova could result in the end of the world, but due the the star’s axis of rotation being tilted away from the Earth this almost certainly debunks the claims.

All that will be left of Betelguese after its impending supernova is a star remnant known as a neutron star. Approximately 20 km in diameter, the neutron star will still weigh more than our own sun and spin incredibly fast – some do in excess of 100 times per second! It is even possible the resulting remnant will be a pulsar neutron star, emitting regular pulses of electromagnetic radiation from the polar regions for many thousands of years (and with such alarming regularity that the pulses might only go out of sync by 3 milliseconds per million years!).

Betelgeuse is clearly visible to the naked eye as a bright red star (it is actually the 8th brightest in the night sky). If you face south and look to the right just after dark, Betelgeuse is the top-left star in Orion (the hunter constellation that resembles a man shooting a bow).

For more information about neutron stars please visit: http://wp.me/p1ZF2o-4G

Written by Chris Phoenix Clarke

4 reasons why astrology is bollocks

by Chris Phoenix Clarke

“I don’t believe in astrology; I’m a Sagittarius and we’re skeptical.”

– Arthur C. Clarke

night skyMan has always been curious about the night sky.  I sometimes picture our distant ancestors roaming through Africa’s Great Rift Valley, gazing up on a clear summer’s night and becoming awash with marvel and wonder at the tapestry laid out above them; much in the same way as I experienced as an awestruck child echoing the sentiments unquestionably felt by Copernicus, Galileo and Newton just a few centuries before.  Never has there been more justifiable a spectacle as unanimously admired throughout human history than the ethereal  magnificence of a starry night sky.

But contrary to what the rather crude title of this blog suggests, it is not with too much ridicule that I refute astrology; I think if more people took the time to look upwards instead of inwards we wouldn’t have half the triviality and petty squabbles we are surrounded by in our every day lives.  I can see how the grandeur of the heavens can be spellbinding enough to trigger belief in a connection between us and the stars, but what was once a genuine search for the meaning of human existence has mutated into a money-making industry based entirely on non-scientific speculation that preys on the vulnerability, insecurity and curiosity of millions of people the world over.

Some may assert an honest interest and/or legitimate pursuit of the ‘science’ of astrology, but I can only assume that what they’re really laying claim to is a deluded kind of hobby, a pseudo-science at best.  Science is the method in which testable predictions can be made about the Universe; to date, not a single one has ever happened by way of astrology.

*DISCLAIMER* Before I begin I want to make it abundantly clear that I realise astrology has many furrows and off-shoots, and I don’t claim to have researched each and every astrological avenue; this blog is merely a broad look at the core principles involved and how they withstand to scientific scrutiny.  I’m sure many astrologers will denounce the credibility of other astrologers’ methods (and visa versa) but rather than pursue semantics, I am addressing the fundamental assumptions on which astrology is founded and why, in my opinion, they lack any shred of validity in today’s society.  If this causes offence, well perhaps you should have seen it in your tabloid horoscopes/tarot cards/tea leaves that a tall, dark stranger would appear and insult your mystical beliefs – in which case you really shouldn’t be very surprised, or indeed offended by, this blog in the slightest.

#1 – What force connects us?

Astrology, in its broadest sense, uses the positions of planets and stars at the time of our birth to predict future events in our lives.  This implies that the planets and stars somehow affect us, physically, in such a way that their position relative to each other (and indeed, us) at the time of our birth has a very real — and more importantly, tangible —  influence over what will happen in our futures.

A physical connection means a force must exist.

The Universe as we know it is composed of 4 fundamental forces: the strong and weak nuclear forces, which act only at very short distances and govern the interactions between subatomic particles and atomic nuclei; electromagnetism, which acts between electrically charged particles, and gravitation, which acts between masses.  Absolutely everything we know of in the entire Universe happens because of one or a combination of these 4 forces at work, and we understand them well enough to send rockets to the Moon, supply electricity to homes, create medicines and technology, and blow up entire Japanese cities.  This doesn’t go as far to say we know everything there is to know, but from the inexorably vast leaps in scientific knowledge through the ages we can safely say we have capitalised on what we do know, and heroic feats have been accomplished by those endeavouring to seek and discover new and unfamiliar advancements of mankind.  So for those that decree an ‘unknown’ force as the puppeteer of astrology I say this: if science, in all its rigour and tenacity, knows nothing of this force by now, then I can assure you that practitioners of astrology know even less.

It seems only logical then to discount the nuclear forces, due to their inherent proximity limitations, and concentrate instead on gravity and electromagnetism as possible candidates for the mystery force of astrology.

If the supposed connection between us and the planets was down to gravity, then due its own definition the gravity experienced between a human and a planet would be proportional to the two masses involved and inversely proportional to the square of the distance between them.  This means that both mass and distance are defining characteristics of the ‘force’ of gravity (Newton proposed gravity as a force; Einstein later postulated that gravity is simply the act of falling into the curved spacetime caused by a massive object – see a previous blog ‘Once upon a spacetime).

This raises two very important points: 1) if gravity is the force used by the workings of astrology then any object of mass will affect the predictions; moreover, the larger the object, the larger the force of gravity.  2) the distance between an object and the Earth is also vitally important; the further away something is the less ‘pull’ of gravity it exerts.  The implications are therefore very clear; objects with more gravity in relation to the Earth exert a higher force, meaning they should have more influence in astrological terms.

However, as will become repetitively apparent, this couldn’t be further from the truth.

Jupiter, for example, holds no more sway than Saturn even though it is much nearer and far larger.  Diminutive Pluto, barely even two-thirds the size of our moon, has no less say-so than Mercury even though it is a few billion miles further away from the Earth.  Seemingly exempt are also the various moons, other dwarf planets, and asteroids of the Solar System; indeed, two moons outsize the planet Mercury and a further five outsize Pluto.  The dwarf planets Eris and Makemake are comparable to that of Pluto and there are many other TNOs (trans-Neptunian objects) well over two hundred miles in diameter, usually found in a region known as the Kuiper Belt (a vast reservoir of asteroids, similar to the asteroid belt between Mars and Jupiter, but found much farther out past Neptune).

Solar system objects to scale
Solar system objects to scale
The main planets and dwarf planets to scale
The main planets and dwarf planets to scale

So knowing what we do about gravity, it does beg one glaringly obvious rhetoric: surely the Moon, being as massive and as close as it is, would have the only influence over our lives?  The other planets (somewhat larger than the Moon, granted, but are so much further away than they are more massive) exert next to no gravity in comparison, so how would they have any influence whatsoever over our lives when pitted against the huge rock on our cosmic doorstep?  It’s like saying a lit match several fields away has equally as likely a  chance to burn you as the raging bonfire you are swigging your cider next to.

One might go so far as to say that the actual planet we reside upon exerts more gravity than anything else; the very fact we remain rooted to the spot as the Earth spins at 1000 kph attests to it, and yet the colossal mass directly in contact with our feet has about as much input into astrological predictions as a penguin does in an avalanche.

Of course the real nail in the coffin for gravity being the solution to astrology is its inherent weakness when compared with the other three forces.  It is so much weaker, in fact, that a simple fridge magnet can beat the entire Earth in a tug-of-war with a paper clip.  Not even the whole of the Earth’s mass, pulling at the paper clip gravitationally, can stop the humble magnet from picking it up.  This shows just how superior electromagnetism is as a force when compared to the strength of gravity.  To suggest the planets can gravitationally affect our futures due to conditions set when we were born is, quite simply, barking ludicrous.

So what about electromagnetism then?  The problem with this theory is that electromagnetism deals with the interaction of electrically-charged particles, either in the form of electric or magnetic fields, and because of the composition of the various planets, not all have electric or magnetic fields – they can be neutral.  All the planets would need to be equally ‘charged’ for any astrological predictions to be made and as far as is known to science — and more importantly, astrologers — this just isn’t so.

In any case, by far the largest emitter of anything electromagnetic is the Sun itself.  Making up over 99% of all the mass in the Solar System, the Sun dwarfs anything else in the neighbourhood and if electromagnetism is the source of astrology’s mysterious force, then any and all predictions about our futures would only deal with the Sun and nothing else (to do otherwise would be akin to thinking that spilling a glass of water during a tsunami made a noticeable difference).  Again, this is not so in astrology.

#2 – why some ‘planets’ and not others?

There are more than just 9 (pardon, 8) planets.  Pluto’s declassification as a ‘proper’ planet was bad enough for astrologers, but since then many other Solar System objects, comparable in size, have been discovered, with undoubtedly many more on the cards.  Unless astrologers grant some special pass to the main 8 planets, why should they be dealt with any differently to any other object orbiting the Sun?

We already established that gravity – or more precisely, mass and distance – cannot figure in astrology, and this isn’t an opinion; this is according to astrologers themselves and the way they treat each planet equally when formulating predictions.  So by their own admissions, astrology cannot be based in gravity.

So if mass and distance are redundant and the only factor of importance is proper classification as a planet, then what do we do about the hundreds of new planets that have been discovered orbiting other stars in our galaxy?  Distance clearly plays no part, and these newly discovered planets are proper planets, so why shouldn’t they figure?

#3 – The falsifiability of star sign astrology

If science has been dropping bombs on ignorance, stupidity and mumbo-jumbo over the last few centuries, then the one about every person on the planet being the wrong star sign has got to be up there with other great explosions of scientific sanity such as carbon dating and the Earth being spherical.  Yes, when I first heard this it amused me too.  The fact that there are actually 13 signs in the zodiac only added more sprinkles to an otherwise already very tasty slice of cosmic in-your-face cake, which I shall now explain.

There are 3 critically-essential problems with the branch of astrology commonly found in newspapers and magazines.  Star sign astrology, or horoscopes, deal with the apparent position of the Sun relative to a set of constellations when someone is born (otherwise known as the zodiac).  They claim that being a particular star sign assigns someone particular and specific traits about their personality, and allows for the determination of certain future events in their lives – usually days, weeks or months in advance.

The first problem is that of axial precession.  If the Earth was perfectly spherical all the time then it would spin about its axis and demonstrate no ‘wobble’ whatsoever – kind of like the wheel of a new car as it spins around the axle.  But due to the Earth bulging slightly at the equator and the fact that the Sun, Moon, and other planets tug at it gravitationally, the spin becomes ever so slightly offset and over the course of approximately 26,000 years the Earth’s north direction traces out a complete, but small, circle in the night sky.  Analogous to this would be a spinning top when slightly off-balance; the toy would begin to wobble away from dead-upright and trace a small circular motion about the centre (but of course spinning tops obey friction laws and the Earth’s gravity, and so the circle becomes larger and larger until it topples over).

This means, many years from now, that Polaris (the North Star) will no longer be our northern reference point in the sky; instead it will move towards the stars Deneb and then Vega, before returning once more to Polaris (see animation below).  This precession causes the apparent position of the Sun against the backdrop of the constellations to move over time, meaning that the Sun will not always be in the same sign of the zodiac at the same time each year.  Furthermore, over the course of 26,000 years the Sun actually regresses through each one of the zodiac constellations until it is back where it started, meaning that astrology’s dependence on the position of the Sun relative to the stars is complete and utter nonsense.

This stellar regression has resulted in star signs shifting forwards in the year by about a month since the zodiac was conceived 2000 years ago, so pretty much everyone alive is now a different star sign; Cancers are now Gemini, Capricorns are Sagittarius  and so on and so forth.  Those born in the first half of December might be intrigued to know that they are actually Ophiuchus, the ’13th’ sign of the zodiac.  Left out by astrologers in favour of only wanting a collection of 12 star signs, Ophiuchus is evident in the sky for all to see but is seldom spoke of, lest known or accepted, by astrologers and the general public alike.  Just another example of astrology cherry-picking and ignoring the evidence put forward by astronomers.

Axial precession
Axial precession

The second problem concerns the movement of the stars over time.  All stars in the Universe career through space at astonishing speeds, bound by the force of gravity as they orbit the centre of mass at the centre of their respective galaxies.  Stars in our own galaxy–the Milky Way–are not fixed relative to the Earth.  They are moving relative to us and we are moving relative to them; it only seems like the stars are continuously found in the same place each year because of the immense distances involved.  You only have to look out from the beach to a small boat on the horizon to see that it appears to barely move.  It gives the illusion of staying still even when crashing through the waves at a given rate of knots.  After a short while you might notice a small degree of movement to the left or right, and this is analogous to the astronomical time it would take for a star many light years away to appear to have moved in the sky at a given rate of tens of thousands of miles an hour!  Every single one of the constellations we see now looked completely different to the dinosaurs and will look completely different in the future, thus rendering star-sign astrology and its dependence on the zodiac totally falsifiable.

Thirdly, a process known as cognitive bias can occur because of the vague and highly ambiguous predictions of star-sign astrology.  A bit like television weather forecasts, the outlook for a given region can only be honed-down to the precision of ‘widespread gales with a chance of rain’, or ‘patches of cloud’ and ‘sunny spells’.  The same is evident in all horoscopes ever written.  ‘Your luck will turn’, ‘beware of financial problems, ‘you will meet someone who does something’ are all common ‘predictions’ of horoscopes and yet they are so vague it is any wonder why people take the slightest notice.  The deliberate ambiguity only heightens the inherent lack of legitimacy.  Cognitive bias is the process by which people act upon what they have heard.  So in other words, after hearing they might be lucky or make some money, or meet someone, they will subconsciously go out of their way to make it happen.  This might take the form of taking more chances to become lucky, or deciding to go to a nightclub after all, thus increasing the chances of ‘acting out’ their horoscope.  This applies to the traits assigned to their star sign too; an individual who is a Cancer might grow to fit their profile as outlined by astrology because they subconsciously think it’s the way they are meant to act.

There is also one strikingly obvious flaw with star-sign astrology.  Assuming that statistical averages hold true (and they always do when dealing with large numbers) this means that roughly an even amount of people are born into each star sign, meaning that if we divide all the 7 billion people of this planet into the 12 [accepted] signs of the zodiac, there will be over 580 million people with the same star sign as you.  Suggesting that my weekly horoscope in the Daily Mail applies to 580 million other people makes the prediction of me coming into financial success that little bit less fortunate (not to mention economically unlikely!).  Also there are only so many tall, dark and handsome strangers on this planet!

Finally, if astrologers choose to ignore axial precession and the movement of distant stars, they cannot dispute that each orbit of the Earth around the Sun does not bring it back to exactly the same spot.  On average, the Earth is 44,000 miles further away each year, implying that someone born on the same day as you the following year would not have been in the same position as you were in relation to the Sun.  Again, this throws the validity of astrology right out the laboratory window.

#4 – Consistency, consistency, consistency!

If a mysterious force as of yet known to science–but somehow understood and utilised by astrologers–really does exist between humans and the stars, then proof would be in the planetary pudding, so to speak.  This would take the form of a certain level of consistency between predictions made by astrology as a whole; and yet there is not one slice of this pudding anywhere to be seen.  In fact, some statistical tests have debunked the claims of astrology so heavily that it’s been stated that pure chance has, in many instances, been more consistent than astrological predictions (Dean and Kelly, 2003).  And that doesn’t even make mathematical sense!

You only have to compare weekly horoscopes between various magazines, newspapers and television shows to see the inconsistencies.

Astrology, clearly and indisputably debunked.

It is often said that recollections of certain memories are finite, that experiences you thought inexhaustible at the time are actually more precious than you know.  Included in this I would undoubtedly put the memory of a crystal-clear, star-filled panoramic view of the night sky.  I’m sure as children  most of us spent some time peering upwards after dark with all sorts of questions about the Cosmos reeling through our curious brains.  But when was the last time, post-childhood, we remembered such an experience?  I know a certain percentage of you will recall — probably with a certain nostalgic fondness — a time spent with friends outside on a clear night, lying on some grass, gazing up at the stars and trying to differentiate between planes, shooting stars and UFOs, but how long ago was it?  And more importantly, how many times will you ever experience it again?  Is it inconceivable then, in the most regrettable of ways, that this particular childhood memory might be the last, or indeed only, time you’ve ever spent really appreciating the starry night sky?  How long before the memory fades into obscurity and is lost forever?

What is now and what was surely a glittering display of celestial magnificence in the times of our first ancestors, the stars are rightly a spectacle to be cherished and used as a catalyst for imagination and discovery.  There is absolutely no need to conjure an imaginary bond between us and these amazing objects, much like the unnecessary invention of gods we seem to require to assign meaning to our lives.  It should be enough that we are able to bear witness to the view, and as science delves deeper into the mysteries of the Cosmos, so too do we learn more about the Universe in which we live, and ultimately about ourselves in the process.

Written by Chris Phoenix Clarke

What looks like a star-filled sky is actually the Hubble telescope's most distant image ever recorded. Each point of light is an entire galaxy, formed in the early universe!
What looks like a star-filled sky is actually the Hubble telescope’s most distant image ever recorded. Each point of light is an entire galaxy, formed in the early universe!

References:

Dean, G., Kelly, I.W., 2003. Is Astrology Relevant to Conciousness and Psi? Available at http://www.imprint.co.uk/pdf/Dean.pdf

The Christian Science Monitor, 2011. Why astrology is even sillier than we thought. Available at http://www.csmonitor.com/Science/2011/0113/New-zodiac-signs-2011-Why-astrology-is-even-sillier-than-we-thought

 Wikipedia, 2012. Axial precession. Available at http://en.wikipedia.org/wiki/Axial_precession

The violent universe: Pulsars, magnetars and neutron stars (and why god did not invent them)

by Chris Phoenix Clarke

“Knowledge of the existence of something we cannot penetrate, of the manifestations of the profoundest reason and the most radiant beauty – it is this knowledge and this emotion that constitute the truly religious attitude; in this sense, and in this alone, I am a deeply religious man.”

– Albert Einstein

There is a lot to be said for the creationist’s view of the Universe.  Design by a supernatural creator — or intelligent design for want of a better term — suggests that all things were crafted according to the blueprints drawn-up by the great architect in the sky; a  power so fantastic, it is beyond our human comprehension.  It’s a very nice thought – albeit one that reeks of unapologetic convenience.

In the history of mankind, invoking the supernatural has often been the case when dealing with the unexplained or the unknown; people can’t explain what they don’t understand.  Inventing a supernatural creator is just a nice and tidy way to account for all that there is, without the need for messy and complicated details.  If this ‘god hypothesis’ is questioned?  No matter!  You can’t speak to them directly or see any physical evidence for it, but books compiled by faceless men thousands of years ago promise wonderful and everlasting afterlives upon receipt of blind faith in these inherently elusive, but supposedly ubiquitous and omnipresent entities.  The same ilk of whom claimed just a few hundred years before that Zeus et al resided atop Mount Olympus, and a thousand years prior, that the sun-god Ra wept and moulded Man from his own tears.  It might very well be the case that these religious scribes believed in what they were purporting, but one cannot simply rule out the possibility of deliberate obfuscation at work; for example, it has long been the opinion of many that Christianity was formulated for the sole purpose of uniting the Roman empire.  But as with most historical accounts, it’s validity is fated to be peppered in ambiguity and inaccuracy – deeming it forever unknowable.

Religion, then, appears to have all the ingredients of a foolproof plan, but a plan that, ironically enough, seems to only have the foolish fall for it.

And so it does beg the question:  why would a god so wise and wonderful possibly feel the need — or indeed, be devoid of any logic and rationality — to create the parasitic Cordyceps fungus that possesses the rather gruesome trait of sending its host mad, before–in the case of the bullet ant–steering it up a tree, spellbound, so as to slowly dissolve whilst the fungal spore grows out the back of its head?  Charles Darwin even used one family of parasitic wasps as evidence for natural selection, writing to a colleague: “I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of caterpillars.”

An ant inflicted with the Cordyceps fungus. Image credit: Erich G. Vallery, USDA Forest Service
An ant inflicted with the Cordyceps fungus. Image credit: Erich G. Vallery, USDA Forest Service

This does not sound like the handiwork of a perfect, all-knowing, all-powerful creator to me.  This sounds more like the harsh, inevitable consequence of millions-of-year’s worth of natural selection as the biological cogs of evolution grind by.  Why, indeed, do humans possess a coccyx bone and appendix?  Much does not add up, and it’s not just restricted to our planet.

Removing ourselves from the weird-but-not-always-so-wonderful demonstrations of nature on Earth, we encounter all sorts of strange and bizarre creations out in space:  the icy rings of debris circulating Saturn; the triple-Earth-sized hurricane tormenting Jupiter, or the toiling great nuclear furnace — our Sun — radiating light and warmth out into the Solar System so we may have the chance to question our very existence within it.  Removing ourselves further, it gets stranger still: not just our Sun, but a hundred billion other stars maraud together around a supermassive black hole at the centre of the Milky Way — resembling some kind of enormous cosmic roundabout — silently and without choice obeying to the behest of  Grandfather Gravity.

These supermassive black holes may indeed be the epitome of extreme, but as of yet we can only observe their effects when we look at the surrounding matter.  We know they are there, but by their very nature they do not radiate light and are therefore unobservable, so I’ll leave the black hole blog for another time and instead focus on what we can see, and trust me – the following are equally as terrifying and just as mind-blowing!  It is inconceivable, then, to think that the very same gods mentioned earlier would go to such vast lengths to create the pure fury and sublime chaos of these awesome monsters.

Neutron stars

Neutron stars are the rapidly rotating remnants of core-collapse supernova explosions – in particular, for stars having been more than 8 times the mass of the Sun.  A supernova explosion occurs when a star exhausts all of the fuel in its core and is no longer able to sustain the fusion process, resulting in the inward pull of the star’s immense gravity exceeding the outward pressure created by nuclear fusion, thus causing the star to collapse in on itself.  In a split second, the bulk of the star’s mass implodes in towards its centre at speeds approaching 23% of the speed of light (155,000,000 mph) creating unfathomable pressure and temperatures of over 100 billion degrees Celsius.  The atoms in the core — fused to iron by this point — can undergo no more fusion and, as they are forced closer together during the collapse, their electrons are forced ever closer towards the nuclei of the atoms and end up combining with the protons to become neutrons.  The neutrons then recoil with an amazing burst of energy – sending out a shock wave that obliterates the star’s outer layers–or envelope–into space.  The reason for this is down to a principle of quantum mechanics called Pauli’s exclusion principle which states that no two fermions can occupy the same quantum energy state.  Broadly speaking, this means that two or more neutrons (themselves fermions) with the same attributes cannot occupy the same space at the same time and are therefore unable to collapse any closer together; consequently, the energy from the collapse is rebounded outward as a supernova.

Composite optical/X-ray image taken by the Chandra Space Observatory showing the pulsar at the heart of the crab nebula.
Composite optical/X-ray image taken by the Chandra Space Observatory showing the pulsar at the heart of the crab nebula. Image credit: NASA/CXC/ASU/J. Hester et al.

All that remains of the star following the supernova explosion is a super-small and super-dense spinning ball of [mostly] neutrons.  Although relatively tiny — approximately city-sized — the neutron star possesses mass comparable to that of the Sun, meaning that it’s density is so extreme that a teaspoon-full would weigh no less than 5000 billion kilograms!

Neutron stars can spin extremely fast.  Unimaginably fast.  The reason for this is due to a law of physics known as the conservation of angular momentum.  Much in the same way as an ice-skater — upon bringing her arms in during a pirouette — speeds up her rotation, so does a star as it transforms from roughly a million miles wide to about 15 miles wide after a supernova.  All the angular momentum the star possessed before (as it spun on its axis like the Earth does each day) is then concentrated and magnified as it shrinks in mass, causing its rotational speed to increase.  It’s hard to imagine, but something the size of Brooklyn, New York weighing more than our own Sun can actually rotate, fully, in excess of several hundred times per second!  Indeed, the current record [recent discoveries pending] for neutron star spin is 712 times per second – 6 times faster than the maximum RPM of most road car engines but a SHED LOAD larger, meaning the rotation clocks in at a quarter that of light speed.  You might wonder why it simply doesn’t break-up and fly apart into space; this is because the inward gravitational forces acting on the star — due to it’s extreme density — overcome the centrifugal forces pulling it outwards (although it is claimed the most rapidly spinning neutron stars become oblate spheroids – or ‘satsuma-shaped’).

There are certain physical limits that govern the behaviour of dying stars.  The Chandrasekhar limit states that the fuel-spent cores of stars can only sustain 1.4 times the mass of the Sun (2.9 × 1030 kg); any more and the electrons give way to the pressure, forcing them into the nuclei of the atoms and combining with all the protons to form neutrons (hence, a neutron star).  If they are under the 1.4 solar mass limit they can end their days in the relative tranquillity of a white dwarf star and do not undergo core-collapse; instead, they quite un-spectacularly  shed their outer layers into space leaving behind a star remnant about the size of Earth.

Larger cores of dying stars are alleged to bypass the formation of neutron stars entirely and collapse straight into a black hole.  Intuitively, these sinister creations are even denser than neutron stars, so much so that their gravity requires an escape velocity greater than that of light – making any attempt at escape impossible.

It is theorised that neutron stars, too, have a limit of mass.  An existing neutron star might accrete matter from a nearby or wayward star and upon exceeding a certain upper limit of mass — known as the Tolman–Oppenheimer–Volkoff limit — the theorised quark star is formed where the neutrons break apart into their constituent quarks.  This process still abides by Pauli’s exclusion principle, but it is now the quarks — who are themselves fermions — that the principle shifts to.  Quarks are believed to be the final ‘Russian doll’ in the particle set; that is, they can get no smaller and are therefore indivisible.  As the neutrons break apart and the star collapses inwards, the quarks get squashed together until they too cannot violate the principle and collapse is halted and produces a quark star.  It is not known whether this collapse generates a smaller supernova of sorts or not.

Pulsars

Pulsing neutron stars–or pulsars for short–are both the lighthouses and the Swiss watches of the Universe.  They are neutron stars that emit vast, concentrated bursts of electromagnetic radiation from their magnetic poles, usually in the radio and x-ray ranges of the spectrum, and are generally caused by the fastest spinning neutron stars or those that have accreted matter from a close, neighbouring star (otherwise known as a binary star system).  The beams of radiation are only visible when they sweep past an observer’s point of view as the star rotates — much in the same way as a lighthouse beam appears to ocean vessels — and due to the wizardly precision at which they spin, they also perform better than any atomic clock developed on Earth!  Indeed, it is estimated that certain neutron stars and pulsars will only slow down by 10−15 seconds per rotation, meaning that [for argument’s sake and ease of comparison] a pulsar with a 1 second rotation will slow to 1.03 seconds after one million years!

A pulsar emitting jets of radiation from its poles

Magnetars

Sounding like a prehistoric monster made entirely from magnets, this third incarnation of a neutron star is rightly considered as the ‘Mad Uncle’ of stars.  Not one thing about a magnetar hints at any snippet of logic, sense or purpose, and goes to show what a barmy, chaotic and violent place the Universe really is.  Although more is yet to be discovered about magnetars, it is believed they are a very brief phase in the lifetime of a pulsar; some scientists speculating that they are formed immediately after a supernova and live for about 10,000 years until the star transforms into a pulsar.  ‘Blessed’ with the strongest magnetic fields known in the entire Universe — they are a trillion times stronger than the Sun’s and up to 1000 times that of an ‘ordinary’ pulsar — their force is such that a magnetar at the Moon’s distance away (250,000 miles) would wipe every single bank card on the planet.  The same beams of radiation seen emanating from pulsars are also a feature of magnetars, but due to the hellish conditions caused by the crushing magnetism the star’s turbulent interior allows for the emission of gamma rays — the most powerful type of radiation in the Universe.

Like pulsars, these jets of gamma rays are restricted to the north and south magnetic poles, but probably the most violent attribute of a magnetar is its ability to erupt enormous gamma-ray flares from anywhere on its surface thanks to a phenomenon known as a star quake.  The imposing magnetism of our own Sun is responsible for its internal and surface disturbances and quite often results in magnetic field lines snapping to release solar flares.  Now imagine a star with magnetism a trillion times more powerful (that’s 1,000,000,000,000 – or 1 followed by 12 zeros!).  When these magnetic field lines snap, the flares that are produced are so powerful and so energetic that they can only manifest in the form of gamma radiation.  Moreover, the current record for the brightest radiation ever recorded is from a magnetar flare which blanketed the Solar System in 1979 – 100 times more powerful than anything witnessed previously.

And so…

If there is one thing I would want people to take away from reading this, it would hopefully be some new-found awareness of the majesty of the Universe.  Not down to it’s beauty or simplicity, but because of it’s ferocity, chaos and complexity.  A creator didn’t design or sculpt these amazing beasts, just as much as one did not have a hand in the process of the evolution of parasites.  The incomprehensibility of the immense forces at play regarding pulsars, magnetars and neutron stars is overwhelming in itself, but just as valid is the question concerning the purpose of it all.  Why would god design such constructions that ooze of excess and unnecessity, that possess chaos and fury in such ways that we may never understand them or the reasons behind?  And if there is a purpose to it all, a reason for their existence, then it certainly isn’t written in the books of organised religion here on our unremarkable little planet, situated on the outskirts of a typical galaxy, just one of several hundred billion in the observable universe.  If a god or supernatural power ignited the spark at the beginning of time and space it most certainly was not for our benefit, and I find it arrogant and somewhat insulting to every other star or planet out there that we might believe it to be so.

The Universe is beyond reach and beyond comprehension, but as soon as we stop putting faith in fabricated and fictional creators the sooner we can begin to unlock its secrets, and that, in my opinion, is surely the real meaning of god.

Written by Chris Phoenix Clarke

Callaway, E., 2009. Life: ‘Ancient virus gave wasps power over caterpillar DNA’. New Scientist, [online]. Available at: <http://www.newscientist.com/article/dn16597-ancient-virus-gave-wasps-power-over-caterpillar-dna.html> %5BAccessed 3rd October 2012].

Wikipedia, 2012. Neutron star. Available at <http://en.wikipedia.org/wiki/Neutron_star>[Accessed 4th October 2012].

NASA, 2012. Neutron Stars and Pulsars. Available at <http://imagine.gsfc.nasa.gov/docs/science/know_l1/pulsars.html>%5BAccessed 8th October 2012].

5 roads to Armageddon?

by Chris Phoenix Clarke

Of all the bandwagons of all the ages it is perhaps fitting that the greatest one of all, is, according to its own proclamations, the very last bandwagon in the history of mankind. I am of course referring to ‘2012: Apocalypse Earth’.  You know, the one about the Mayan prophecy, the galactic alignment, judgement day etc.  The media, as you’d expect, are (somewhat ironically) having a field day with this doomsday scenario.  The end of the world, it seems, is a good earner.

Whether it be excruciatingly bad Hollywood blockbusters, sensationalist media reporting, or deluded religious types called Harold Camping, it appears that we all get enveloped in the dazzle and drama of doomsday prophecies one way or another.  Having said that, at the time of writing, interest in the subject has dwindled somewhat but I suspect as the year reaches its inevitable climax the interest will return with a reinvigorated vengeance.

It’s best then, that I try to set a few things straight and give you the chance to make up your own minds about the potential dangers we face. What follows are the most likely candidates, the basic scientific evidence behind them, and the probabilities of them becoming the global catastrophe that has been ‘prophesied’ to be.

Coronal Mass Ejections (CMEs)

Holding the award for the least badly-reported doomsday scenario, the Sun does actually seem to be Public Enemy #1 in 2012.  Like pre-menstrual stress, this is a time in the Sun’s life where it becomes irrationally agitated and angry in regular cycles; although unlike PMS (sadly) this occurs approximately every 11 years and is known as the solar maximum.  Contrary to popular belief, the imminent solar maximum actually reaches it peak in 2013 and not 2012.

As it reaches its maximum, the Sun plays host to increased levels of magnetic disturbance, which, simply put, is where its magnetic field lines become tangled and distorted and eventually snap, releasing billions of tonnes of highly-charged particles into space (this takes the form of a plasma containing mostly electrons and protons and is referred to as a CME).  Every so often the Earth is found in the cross-hairs; a fact that was made evident just 2 solar maximums ago in Quebec, Canada in 1989 where one of these stellar outbursts caused an entire blackout of the city.  This, though, was a mere flesh-wound compared with the one that hit us in 1859.  Scientists claim that had it happened in this day and age it would have knocked-out the entire grid of the Northern Hemisphere.  The Auroras (Northern lights) were even observed as far south as Cuba!

A CME as it erupts from the surface of the Sun

The danger a CME poses is its ability to inundate the Earth’s magnetosphere so intensely that it can no longer ‘keep its shields up’.  The magnetosphere–or Earth’s magnetic field–is tasked with protecting the planet from harmful particles, such as the solar wind, but due to the battering it receives at the hands of a CME its effectiveness is reduced and the harmful plasma filters through to the surface of the Earth.  This influx of charged particles knocks out electric grids; power lines melt and transformers explode thrusting vast areas of the planet into darkness.

But what a lot of people fail to realise is that no electricity = no ANYTHING.  Petrol stations can’t pump petrol, water cannot be pumped to houses… it would literally be anarchy in a matter of days and not weeks.  The real damage though is the recovery time, as there is simply not enough time or man-power to replace all the fried transformers in a quick and efficient manner.  Computer models even suggest it would take decades just to reach a fraction of the operating power we once had, if at all.

All this considered, the same computer models grimly announce that affected countries will suffer population death tolls of 50%, with the total reaching tens or even hundreds of millions.  It is certainly a bleak outlook.  The only saving grace is we would need to take a direct hit from a powerful CME for this to even pose a threat.

Chance of catastrophe happening in 2012: 1/10

Pole Reversal

A pole reversal  is just that: magnetic North and South switch orientation.  The Earth’s polarity changes.  Compasses point to the South.  This potential apocalyptic perpetrator also has sound scientific backing, with evidence in rocks on the ocean floor showing it has happened many times before.  As the tectonic plates which divide-up the Earth jostle for position, it is often the case that the crust pulls apart under the oceans at something called a divergent plate boundary.  This is where two plates move apart from each other causing the crust to tear and new magma to rise-up from deep within the Earth to fill the gap and solidify into rock.  As the process continues over time, the plates continue to separate further apart with this newer rock slowly becoming older rock on either side as new magma rises where this [now] older rock had done many thousands of years before.

Above: the process known as sea-floor spreading.                  Below: the magnetosphere before and during a reversal.

The key, though, is in the way the magma cools.  Magnetic minerals in the magma align towards the Earth’s magnetic field and harden in this pattern.  Upon examination of the ocean floor, scientists discovered a symmetrical pattern on either side of the plate boundary that showed parallel bands of rock alternating between magnetic north and magnetic south at regular intervals of time.  The implications were shocking:  The Earth’s magnetic field actually flips every few hundred thousand years or so, with the last reversal taking place 780,000 years ago and the current phase of magnetism actually being the longest sustained period of ‘non-flipping’ in the last 5 million years.

To say that we are overdue a geomagnetic reversal might be a gross understatement.  The reality, some say,  is that it has already begun.  Others argue that the rocks on the sea-floor show the existence of superchrons; periods of time where the polarity of the magnetic field remains the same for well over 10 million years at a time without reversing.  The most recent was the Cretaceous superchron 120 to 83 million years ago. Either way, one cannot ignore some of the most recent scientific research into magnetic anomalies.  I won’t go into detail, but the basic proof comes from satellite imagery showing areas of the magnetosphere where the field lines are already becoming distorted, and the real ominous news is that the size and frequency of the anomalies have increased in just the last 40 years alone.

The danger of a pole reversal is in its transition.  A complete reversal can take over 1000 years, during which the Earth’s magnetosphere effectively disappears and no longer acts as the protective shield blocking our planet from harmful solar radiation.  This leaves the Earth – and all life upon it – totally vulnerable.  It is not clear what effect this new found nakedness might have; some scientists claim that unless humans adapt to subterranean lifestyles, they will most certainly die from being burned.  This, and the fact that given time, the solar wind would strip Earth of it’s atmosphere – like it did on Mars millions of years ago – thus rendering the air unbreathable and as such, life impossible.  Also plant-life would die, causing food shortages for animals and humans alike, and those reliant on the Earth’s magnetic field lines for navigation would find themselves incredibly disorientated.

A bleak outlook indeed.

Thankfully there are also scientists who assure that there is absolutely no evidence of negative effects due to the omission of a magnetosphere.  Homo erectus (distant relatives of homo sapiens) seemed to manage just fine, and so did the various flora and fauna of the time.  If anything, they claim, the charged protons and electrons that make up the solar wind will actually create a substitute magnetosphere on contact with our atmosphere.

So the jury is still out on this one, and although it is a certainty that it will happen; there is absolutely no chance it will happen in the next few months.  If I had to hazard a guess it would be that the pole reversal – presuming it continues throwing-up anomalies at its current rate – would start to become evident in the next 100 years onwards.

Chance of catastrophe happening in 2012: 1/10,000

Supervolcanic Eruption

Supervolcanoes are enormous, but considering their immense size, few people are even aware of their existence.  And for the 25 or so that are currently known to science, Yellowstone is undoubtedly the most well-renowned, situated in Wyoming, USA (although most people would associate Yellowstone with being a national park and the home of Yogi Bear!).

The Mount Pinatubo eruption of 1991

To classify as a supervolcano, a volcano must be capable of producing an eruption that ejects more than 1,000 km3 of material.  To put this into perspective, the Eyjafjallajökull volcano which erupted in Iceland in 2010 – causing unprecedented aviation chaos over Europe – ejected the comparatively hiccup-sized amount of just 0.1 km3.

Supervolcanoes are the largest type of volcano, producing the largest eruptions and are therefore granted the highest rating on the Volcanic Explosivity Index (or VEI) as a VEI 8.  The Eyjafjallajökull eruption of 2010 was a VEI 4.  Other well known eruptions of recent memory are:  Mount St. Helens (1980) VEI 5, Vesuvius (79 AD) VEI 5, Mount Pinatubo (1991) VEI 6, and Krakatoa (1883) VEI 6.  Incidentally, the cataclysmic eruption of Krakatoa is considered to be the loudest noise ever heard by Man and the magnitude of the explosion was such that it caused global temperatures to drop by 1.2°C and darkened the sky for many years afterwards.  The official death toll was around 36,000 people, but proper estimates suggest that the figure was well in excess of 100,000.  One of the largest tsunami waves ever, measuring 45 metres high, inundated Indonesia as a consequence of the volcano literally blowing itself to bits (to put this into perspective also, the tsunami that hit Japan in 2011 was about 10-15 metres high).

And all this from a volcano of VEI 6.  All supervolcanoes are at least VEI 8.  In other words – in excess of one hundred times larger than Krakatoa!

Edvard Munch’s ‘The Scream’. The most valuable work of art ever to be sold at auction at $120 million. It is thought the sunset depicted was based on the incredible sunsets caused by the 1883 eruption of Krakatoa

If there is one piece of information that might put your mind at ease, it would be the fact that supervolcanoes run in what I call ‘geological time’.  This is to say that eruptions are so far apart that enough time passes for very boring things to happen to rocks.  Yellowstone, as an example, erupts on average every 600,000 years.  The entire history of human civilisation on the other hand, can easily fit into just 2 % of that time (10,000 years) with change to spare.  But without meaning to sound too reassuring, I should probably point out that Yellowstone last erupted over 640,000 years ago!

A supervolcanic eruption has the potential to kill millions of people in the vicinity of a few hundred miles from the volcano itself, and the immense ejection of dust and gases into the atmosphere would cause volcanic winters:  years where global temperatures plummet as a result of the obscuring of sunlight, and eventually a runaway-greenhouse-effect: the process by which the sudden increase in greenhouse gases released by the eruption cause global temperatures to rise.  Indeed, it is proposed that the supervolcanic eruption of Lake Toba, Indonesia in 71,500 BC was very nearly responsible for the eradication of the entire human race at the time.  Scientists believe only a couple of tens-of-thousands of humans survived the cataclysm.

This is a very genuine threat and it really is only a matter of [geological] time until it happens again.  Most supervolcanoes don’t show too much activity, but due to the fact that Yellowstone has a confirmed active – and very large – magma chamber beneath it, and quite regularly changes the lay of the landscape and has hundreds of small earthquakes, I’d say the risk is ‘imminent’.  The only redeeming factor is that warning signs should precede an eruption, and last for some time before the onset.

Chance of catastrophe happening in 2012: 1/100

Gamma-ray Burst (GRB)

The electromagnetic spectrum (if you paid attention in class) is the full-range of all the frequencies at which light propagates – or more accurately: the range of frequencies at which electromagnetic radiation travels – of which, visible light is but a small part of the range.  At the lower-frequency end you have radio waves and microwaves, and at the other, higher-frequency end, you have x-rays and gamma rays.  Frequency of electromagnetic radiation is calculated as the speed of light divided by the wavelength of the radiation.  This means that frequency is inversely proportional to wavelength; the larger the wavelength, the smaller the frequency.  This makes sense, as a shorter wavelength would repeat itself much more ‘frequently’ as it travels through the air than a longer wave, and thus, its frequency is higher.

That’s the science bit over and done with.

High frequency radiation, as the name implies, possesses high amounts of energy; and high energy can be very, very dangerous (as the year 1945 can attest to, if it were politically incorrect).  Gamma rays are the most energetic source of radiation in the Universe and it takes a very spectacular type of event to produce them in vast, concentrated outbursts.  Such events include, but are not restricted to,  the collision (and subsequent merger) of two neutron stars, or more commonly, in supernova and hypernova explosions.  I will concentrate on the latter.

Supernovae, and their ‘go large’ relatives, hypernovae, are the most violent events in existence.  Caused by the death-throws of a dying star, a supernova initiates after the gravitational collapse of the star’s core and obliterates itself in a wonderfully destructive explosion, the magnitude of which means it briefly outshines the entire galaxy it resides within.  But not all supernovae necessarily emit bursts of gamma radiation; it is thought only the most massive of stars do upon exploding.  Massive stars, after undergoing a supernova, usually form a neutron star from the leftovers: a city-sized, incredibly dense ball of matter, spinning unimaginably fast.  Neutron stars have so much mass squashed into such a small space that only one teaspoon of neutron star material would weigh 5000 billion kilograms!  That is the same as having 900 Great Pyramids of Giza stirred into your coffee!

But even more massive stars form what are undoubtedly the most sinister of all cosmic structures:  a black hole.   The leftovers of these supernovae are forced together so tightly that the sheer density of the material causes space and time to literally curve in on itself so much, that nothing entering can ever leave – not even light.

A black hole, spewing out gamma ray bursts from either pole

Both the creation of neutron stars and black holes from supernovae explosions are thought to be the catalyst for the production of GRBs.  The energy released in the processes take the form of jets shooting out straight from either pole, and although only brief – they can be quick flashes, or even bursts of a few minutes – the gamma rays explode-out over vast distances into the unsuspecting Universe.

If Earth was to be unfortunate enough to be in the way of a GRB in our own galaxy, the effects would be devastating.  The side of the Earth facing the burst would be dosed in lethal radiation, and everyone else on the planet would be faced with catastrophic damage to the atmosphere; resulting in an almost-definite mass extinction event.  Indeed, some scientists propose that the Ordovician mass extinction event of 450 million years ago could have been caused by a direct hit from a GRB.

Thankfully, in our own galaxy, a GRB occurs roughly every 100,000 years or so, and the percentage of those that might hit Earth is very low as you’d expect.

Chance of catastrophe happening in 2012: 1/100,000,000

Galactic alignment

The last of the potential doomsday candidates is the increase in gravity experienced by Earth as a result of the so-called ‘impending galactic alignment’.  This increase in gravity is alleged to cause the Earth to be effectively ‘stretched’ from either side, causing the tectonic plates that blanket the Earth to move violently against and away from each other.  The result would be an increase in earthquake frequency and magnitude, and trigger increased levels of volcanic activity – including new magmatic fissures (or tears in the Earth) – each with their own catastrophic side-effects such as tsunamis and volcanic winters.

The galactic alignment idea is, quite frankly, a load of inane and miss-informed sensationalist rubbish.  It is true that the Solar System does transverse the galactic plane every few tens-of-millions of years, but we currently reside several light years ‘above’ the galactic plane and won’t be transversing anything any time soon.  The idea that, from the Earth’s point-of-view, the Sun lines up with the galactic plane is pure nonsense and happens all the time anyhow.

I’m not too sure on the speculation, but I believe some claim that the combined pull of the supermassive black hole (Sagittarius A) at the centre of our galaxy and all the mass of stars along the plane would combine with the gravity of the Sun [as they line up] and cause the increased gravity I mentioned earlier.  Either that or the Earth lines-up in-between the Sun and Sagittarius A and gets stretched instead.  Some proponents of this idea even go so far as to suggest that each of the 5 mass-extinction events that have occurred on Earth have been down to the Solar System’s alignments with the galactic plane.  The problem is there is simply not enough mass, either in the plane, or indeed in the supermassive black hole itself, to cause any terrible gravitational effects on Earth.  The gravity caused by a given amount of mass is inversely proportional to its distance away, meaning something either has to be pretty close or pretty massive to have any effect, and even though Sagittarius A is pretty damn massive, it is simply too far away.  Even if you factor in the effects of dark matter (which I won’t indulge here), it still doesn’t add up.

The Milky Way face-on (left) and edge-on (right). The galactic plane is the horizontal line that passes through the entire galaxy when viewed from the side. The solar system is about 3/4 of the way from the centre, and quite a number of light years ‘above’ the centre line.

Chance of catastrophe happening in 2012: zero

The outlook

It seems the only road to disaster holding any apocalyptic weight is the Sun unleashing a direct CME.  The poles WILL reverse and the Earth WILL play host to a supervolcanic eruption, but there’s no reason to suspect it will happen in 2012.

My next blog deals with mass extinction events, and whether enough time will have elapsed for humans to be technologically-prepared enough before another one hits.  As I’ve stated, it is only a matter of time before something happens again to threaten the survival of humanity.  The question is: will we have had enough time to develop ways and methods to ensure the longevity of our species?  Will we have colonised space?  Will we have found ways to combat potential threats, such as large meteor impacts?

The Universe, it seems, plays dice with our potential survival, and time is the only thing that stands between us and mass extinction.

Do we have enough of it?…

written by Chris Phoenix Clarke

Once upon a spacetime

by Chris Phoenix Clarke

Imagine a lift at the top of the world’s tallest building.  The lift fails and plummets towards the ground.  You find yourself inside this lift, completely weightless due to the lift’s free-fall, with any books and phones you had in your possession seemingly floating alongside you.  Now imagine yourself in the same lift, but this time drifting in the isolation of space.  The exact same effects are observed: you, and anything else in the lift float weightlessly  around wondering what the hell’s going on.  So it begs the question:  from the effects alone, how do you know the difference between being trapped in a lift undergoing free-fall on Earth and being inside a lift floating in space?

Now picture yourself standing in a stationary lift on Earth, feet firmly pressed to the floor, all belongings resting on their appropriate surfaces.  Then, imagine also, being inside a lift in space that is being towed by a rocket accelerating fast enough as to mimic Earth’s gravity.  You find your feet again pressed just as firmly to the floor and are no better at determining your location than you were before.

This thought experiment, the like of which Albert Einstein frequently posited, goes to show how gravity and acceleration are indistinguishable; they are one and the same.  The effects maybe identical but the situations can be very different and clearly depend on where the person happens to be (or as physicists like to say, the frame of reference of the observer).

This was the cornerstone of Einstein’s theories of relativity.

The theory of special relativity

Special relativity is the description of the motion between two or more related locations in the ‘special’ case of uniform motion only.  This sounds quite complicated at first glance, but, to put it more simply, it explains the motion of one frame of reference with another so long as no acceleration in either frame is taking place (uniform motion).  An example of two frames of reference applicable to special relativity would be you, sitting at your computer chair reading this (frame 1), while a bird flies past your window at a constant speed (frame 2).

With me so far?

The theory arose due to Einstein’s realisation that there really is no absolute frame of reference in the entire Universe; everything is moving.  You might feel completely stationary sitting in your chair, but really the Earth is spinning on its axis at almost 1000 kph and in doing so, orbits the Sun at the incredible speed of 65,000 kph.  The Sun, along with the rest of the solar system, orbits the centre of our own galaxy–the Milky Way–in one of the galaxy’s spiral arms.  The Milky Way, too, along with its neighbouring galaxies, is orbiting around the centre of gravity in what’s known as the Local Group of galaxies, which are themselves part of a super-cluster of local groups of galaxies that are marauding apart from all other super-clusters as part of the continuing expansion of the Universe.

…and breathe.

So as you can see from the gravity Russian-doll effect above, there is nothing fixed in the Universe with which to measure motion from; even the empty space between galaxies is constantly expanding.  The only thing with any relevance is something’s motion relative to something else.

The speed of light is just under 300 million metres per second

This brings us to the speed of light (although not literally, as we will see why in a moment).

The actual speed of a beam of light was predicted by Maxwell through his famous equations on electromagnetism 150 years ago and was subsequently confirmed by experiment around the same time.  But the really important discovery about light was that it always propagates at the same speed no matter how it is observed.  In other words, even if a beam of light was shone from a moving car, an observer down the road would measure the same speed for the beam of light as if the car had been stationary.  This is clearly counter-intuitive; the following example illustrates why:

Imagine 2 cars: a red one stationary and a blue one driving past it at 30 mph.  Just as the blue car passes by the red car, a passenger in the blue car hurls a cricket ball out at 60 mph in the direction of motion.  How fast does the cricket ball appear to travel when measured by the driver of the red car?  The answer is quite simply 90 mph.  The velocity of the ball is added to the velocity of the moving car to give a total answer.  Makes perfect sense, right?  Now imagine the scenario where somehow the blue car is whizzing past the red car at half light-speed and the passenger this time throws the cricket ball forwards at the speed of light itself.  Observed from the red car, the driver–according to the previous example–would measure the total velocity of the ball to be 1.5 times the speed of light.  Unfortunately for common sense, this is not the case at all.  The speed of that cricket ball will only ever be the speed of light, no matter how fast the blue car is driving.  The reason?  It’s just a fundamental feature of our Universe and nobody knows why!

The discovery that the speed of light is the same regardless of the motion of the source and/or the observer meant that the view Isaac Newton had proposed a couple of centuries earlier had to be amended.  It also implied that if the speed of light was constant, then the simple act of moving in relation to something else threw up all sorts of peculiar effects, especially when travelling close to light-speed.

Time dilation

Again, you’ll need to picture the following thought experiment:  Two people invent a very simple clock consisting of a particle of light bouncing up and down between two mirrors a fixed distance apart.  It acts as a clock because the distance remains the same and the speed of light is constant between the mirrors.  One person stands still and the other picks up the clock and moves horizontally in front of the stationary person at a given (fairly high) speed.  Rather than see the particle of light move vertically up and down, the stationary person sees it move sideways as well as up and down, in a kind of zigzag fashion looking something like a pattern of the letter WWWWW instead of a pattern of the letter IIIIIII (see below).

As you can see, the light particle on the right travels further to bounce up and down from the perspective of the stationary person.

This implies that the light particle has appeared to have travelled a longer distance between each bounce, but because the speed of light is always the same no matter the vantage point, it also implies that a longer period of time must have elapsed between bounces.  The person who is moving, however, sees no change in the light particle’s motion as he/she is moving along with it.  To them, it is still bouncing straight up and down, exactly the same as when they were stationary.  This means that the clock is running faster for them than what their friend (the stationary one)  perceives it to be.  This leads to an effect known as time dilation, and although the time difference is minuscule when considering most types of movement, it becomes particularly noticeable when an object is travelling close to the speed of light.

An example to illustrate time dilation is an astronaut travelling the 4 light years from Earth to the next nearest star (Proxima Centauri) at 90% of the speed of light, taking a total round-journey time of just under 9 years.  Upon returning home, 20 years would have elapsed on Earth making everyone on the planet 11 years older than the astronaut.  Time travel, it seems, is really quite possible in this sense!  For similar reasons, the astronaut, whilst hitting 90% light speed, would appear to have contracted in length from the frame of reference of the observer on Earth – if it was possible for them to see – and have also doubled in mass  (more on that in a moment).  If this sounds like make-believe to you then you’ll be shocked – and hopefully pleasantly surprised – to learn that these ‘relativistic’ effects are completely real phenomena and are accounted for in particle accelerator experiments (such as the LHC at CERN) and in GPS.

The speed of light is the maximum speed with which an object can travel.  The main reason for this is causality, the process by which cause precedes effect, and states that the reverse is impossible.  Lighting a fuse to detonate a bomb is cause followed by effect; the explosion followed by the lighting of the fuse is effect followed by cause and is quite obviously absurd.  This is why nothing can reach superluminal speeds (faster than light), as observers could witness events before they’ve even happened!

It is also impossible for any object of mass to accelerate to the speed of light.  Due to the effects of special relativity, it would take an infinite amount of energy to accelerate a body towards light-speed as more and more energy would be required to continue to accelerate a body that is becoming exponentially heavier as it speeds-up.  Why would something ‘put on weight’ simply by going this fast?  The answer is found in what is undoubtedly the most elegant and well-recognised equation in history:  E=mc².  This beautifully simple equivalence states, very basically, the interchangeability between energy and mass.  They are, rather crudely, the very same thing.  And seeing as the faster something goes the more energy it has (remember, kinetic energy is the energy something possesses as it moves), then due to Einstein’s equation the mass must also increase.  This means that an object becomes heavier and heavier the faster it goes, thus the need for more energy to keep on accelerating.

The only ‘stuff’ that can travel at the speed of light are massless particles (such as particles of light, or ‘photons’), and they can only travel at this one speed at all times.

Einstein’s breakthrough, then, was to establish not only that the laws of physics were the same in all ‘inertial’ frames of reference (in short, where the observer is undergoing uniform motion) but also that the speed of light is always the same speed no matter the frame. The exotic side-effects he predicted in his special relativity required immense speeds, so what happens in the presence of immense gravity?  We established earlier that gravity and acceleration are one and the same, and if relativistic effects (such as time dilation) occur at high speeds then they can also occur at high acceleration.  Would it be reasonable, therefore, to suggest that the same effects should occur in high gravity also?

The theory of general relativity

Such was the ground-shattering implications of Einstein’s seminal paper that it took him over 10 years after formulating his special theory of relativity to complete it.  It truly is, alongside special relativity, one of the greatest intellectual achievements in science and has been verified countless times by experiment.  That isn’t to say the theory is complete (or even correct), but along with the spooky mechanics of quantum theory it somehow delivers results.

The simple definition of general relativity is the gravitational attraction experienced between objects–such as the Sun and the Earth–is  caused by the  curvature of space.  It says that all objects of mass warp space in the same way that a bowling ball does when placed on a taught sheet of rubber.  So what appears like an actual force of attraction between objects is actually just the process of falling into the curved area caused by an object’s warping of the space around it (formally known as gravity).  And just like a marble being rolled onto the sheet of rubber demonstrating a change of direction as it encounters the curved area around the bowling ball; planets (such as Earth) show the same effects in space.

Light, too, is  ‘bent’ in the the presence of strong gravity and is known as gravitational lensing.  This is where light from a background object follows the curvature of space caused by a nearer object and is focussed towards an observer, just like a lens does, and sometimes causes multiple images of the same object to appear (or even a distorted ring right to appear around the nearer object) to the observer.

Light from a background object is bent around a nearer object due to the curvature of space
4 images of the same quasar appear in the picture

It also allows for the observation of objects that would otherwise have been obscured from view, as the light – had it not been bent towards us – would not have penetrated our field of view and would literally be hidden behind whatever it was that was blocking it.  I should probably point out that the light isn’t actually bent as such — rather it continues to travel in a straight line like it always does, but due to the curving of space around a large object, it follows the curved path of that space and just  appears to bend.

Probably the most remarkable prediction of general relativity is the concept of gravitational time dilation.  Recall the first couple  of paragraphs where I introduced the thought experiments involving lifts.  It highlighted how being accelerated and being in the presence of gravity are indistinguishable from one another and, going on what we learned about special relativity in the section before, should both demonstrate ‘relativistic’ effects.  And this is exactly what does happen!  Satellites orbiting 30,000 km above the surface of the Earth experience less gravity than you or I do standing on the surface.  This is because the curvature (or warping) of space is greater nearer the Earth and less the further away you get, meaning time runs ever so slightly faster for satellites than it does for us; a time dilation effect that has to be accounted for when GPS is used, for example.

This brings up another remarkable concept — that of spacetime.  If time can be altered by the presence of gravity – or rather by the curvature of space caused by a massive object – then it is redundant to consider space and time as two separate entities.  The 3 dimensions of space (height, width, length) and the ‘temporal’ dimension we call time, are therefore classified as one single, 4-dimensional entity known as spacetime.  This is hard to visualize, so it’s probably better not to.  Instead, it would be more prudent to understand that time and space are inextricably linked and that ‘movement’ through one is also movement through the other.

What this concept does imply, however, is the existence of black holes — objects so dense and so massive that the spacetime in which they sit is warped so severely that anything passing by literally falls into this curved space, never to be seen again.  Even light itself cannot escape the gravitational chasm that is a black hole.  Again, we established before that gravity is the same as acceleration, so just like time seems to slow down when an object travels close to light-speed, so does it in the presence of very strong gravity (like a black hole).  It’s been a few paragraphs since the last thought experiment, so here’s another:

Picture an unfortunate astronaut aboard a spaceship that has ventured too close to a black hole (Einstein himself said only two things in life were infinite: the Universe and human stupidity, but that he wasn’t sure about the Universe).  Viewed by an observer at a safe (considerable) distance away, the spaceship would appear to slow down and come to a complete stop, frozen in time.  But from the point of view of the astronaut on the spaceship, time would continue to run like normal; they would continue to move into the black hole until they met their grizzly death of being torn apart by gravity.  If, before they fell in past the point of no return–known as the event horizon–they were to look at the observer watching them, they would see time whizz by at ever-increasing speeds.  The witnessing observer at the safe distance would grow old and die, civilisations would rise and fall, and planets, stars and galaxies would come in and out of existence as time marched on.  And all of this in the briefest of moments as experienced by the stupid astronaut — such is the effect of time dilation.  For the same reason, travelling at nearly light-speed would also give the effect of time standing still as everything else would age incredibly fast (as explained above in the special relativity section).

The curvature of space caused by the enormous mass of a black hole (2-dimensional depiction)

Einstein’s legacy

What Einstein accomplished with his special and general theories of relativity is nothing short of a miracle.  The fact that his one and only Nobel Prize was awarded for something else entirely is one of the scientific crimes of the century!  The beautiful simplicity of his mass-energy equivalence E=mc² led to the understanding of radioactivity and the development of nuclear power, and his insight into the effects of relative motion based on the constancy of the speed of light allowed for the development of the Global Positioning System (GPS).  But most of all, it was his ability to ignore what everyone else was doing and derive his brilliantly crazy theory of general relativity; an outstanding intellectual achievement that has inspired generations of scientists to think outside the box ever since.  It describes the behaviour of everything in the Universe, from the projectile motion of a cannon-ball on Earth to the motion of large groups of galaxies billions of light years away and predicts strange and violent objects such as super-massive black holes.

The only drawback with general relativity is that it is not complete.  That is to say it does not sleep well with quantum theory — the study of the Universe on its smallest scales.  This is most definitely a blog for another time, but the basic problem is that both theories work for their own scale; quantum mechanics for its atomic and sub-atomic particles, and general relativity for everything larger we can see with our eyes.  Neither work for both.  There is no unified ‘quantum theory of gravity’ to explain absolutely everything in the Universe.

For now then, we will have to continue using both.  The one thing I can say with utmost certainty is that if you thought relativity was mind-bending enough, wait until you encounter the weird and wonderful effects of the quantum world.

Written by Chris Phoenix Clarke

References:

Cox, B., Forshaw, S., 2009. Why does E=mc²? (and why should we care?) 

Wikipedia, 2012. Introduction to general relativity. Available at http://en.wikipedia.org/wiki/Introduction_to_general_relativity

NOVA, 2012. The legacy of  E=mc². Available at http://www.pbs.org/wgbh/nova/physics/legacy-of-e-equals-mc2.html